In daily life, people generally use a wiping rag to wipe and clean a small piece of glass, while a rod-type glass cleaning wipe is usually used to wipe and clean a big piece of glass and the external facade of a window. However, while a person is wiping a glass using the rod-type glass-cleaning wipe, he or her arms may easily get tired. In view of this problem, a window-cleaning device with a single suction cup which is now commercially available is capable of cleaning a high-level glass curtain wall. Such window-cleaning device is attached on a vertical wall surface by a vacuum suction cup and is independently driven to run by a wheel or track. However, the above-mentioned single-sided window-cleaning device has a defect as follows, while the wheel is rolling, the portion between a vacuum chamber and the wall surface is in the state of sliding friction, so that the sealing gas is inevitably leaked. In such case, if the glass-wiping device further encounters a gap or more small bumps, gas leakage may be easily caused, which leads to an atmospheric pressure unbalance. As a result, the device can not ensure sufficient vacuum pressure, thus may fall off from the wall surface.